What is a Plasma?

Abstract

Plasma is matter heated beyond its gaseous state, heated to a temperature so high that atoms are stripped of at least one electron in their outer shells, so that what remains are positive ions in a sea of free electrons. This ionization process is something we shall study in more detail. Not all the atoms have to be ionized: the cooler plasmas used in plasma processing are only 1–10% ionized, with the rest of the gas remaining as neutral atoms or molecules. At higher temperatures, such as those in nuclear fusion research, plasmas become fully ionized, meaning that all the particles are charged, not that the nuclei have been stripped of all their electrons.